[GHC] #11334: GHC panic when calling typeOf on a promoted data constructor

[GHC]

#11334: GHC panic when calling typeOf on a promoted data constructor
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        Reporter:  RyanGlScott       |                Owner:  goldfire
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler (Type    |              Version:  8.0.1-rc1
  checker)                           |
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash                              |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D1757
       Wiki Page:                    |
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Changes (by simonpj):

 * owner:  bgamari => goldfire


Comment:

 > I suppose it would be reasonable to set all kind variables of kind * to
 be *, and use Any for the others. We don't want to just use Any all the
 time, because that wouldn't be backwards compatible and defaulting to * is
 quite sensible.  The other reasonable way forward is to issue an error at
 `Proxy 'Con` without having more direction

 I think I favour:
  * Default kind vars of kind `*` to `*`
  * Don't default others; instead error.

 But note that if we have `{k1:k2, k2:*}` then defaulting `k2` to `*` might
 mean we could then default `k1`.

 We do need to do deafulting somehow because even without `PolyKinds`
 consider
 {{{
 data T f a = MkT (f a)
 }}}
 We get `{f :: k -> *, a :: k}` and we can't reject the program.

 Anyway, Richard, thanks for saying you'll get to it.

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11334#comment:18>
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